Beginning work on cleaning up the introductory shader tutorials.  Basically separating out the various component calculations into reusable functions and making it possible to use generic scenegraph objects for the geometry to be displayed.  Working on that because it really seems that beyond a certain point there's diminishing returns in working on the shadow tutorials using legacy entry points.

I'm thinking I'll want to introduce a better Light node for the VRML97 scenegraph to make the full range of the algorithm available.  At some point also need to do a "basic textures" tutorial in the shaders series, likely *before* I start into a shadow-texture tutorial there.

Also need to figure out a portable way to do the shadow-lookups, I'm guessing it's going to be a function such as "float shadowMultiplier( coord, matrix, sampler )" which the shader-compiler will turn into something like: light_shadows[ 1 ] = shadowMultiplier( coord, light_shadow_matrices[1], light_shadow_tex_1 ); that is, do textual expansions so that we don't need a texture-array extension to be available to do single-pass shadowed lighting.